Alkylation of polystyrene using a hydrogen fluoride catalyst



Patented Sept. 25, 1951 ALKYLATION OF POLYSTYRENE USING A HYDROGENFLUORIDE CATALYST John Mann Butler, Dayton, Ohio, assignor. to MonsantoChemical Company, St. Louis, Mo., a

corporation of Delaware No Drawing. Application May 27, 1948,

Serial No. 29,648

This invention relates to a method of preparing alkylated polystyrene ofhigh molecular weight.

More particularly it relates to a method of improving alkylatedpolystyrene for use in modifying lubricating oils.

It is well known that polystyrene compositions may be alkylated byreaction with alkyl halides or olefinic compounds in the presence ofFriedel- Craft catalysts. A wide variety of catalysts have been used,but many are objectionably expensive, others which are more readilyavailable do not produce alkylated polystyrenes of optimum quality, andsome are diflicult to remove from the product. The preparation ofalkylated po ystyrenes with boron trifluoride is known, but suchreactions are frequently diflicult to control and non-reproducibleresults are frequently encountered. Aluminum trichloride is widely usedas the alkylation catalyst, but the product so obtained is oftendegraded and the molecular weight decreased, unless special precautionsare taken. In copending application Serial No. 670,041., filed May 15,1946, by John M. Butler and Joachim Dazzi, there is described andclaimed a method of preventing degradation during alkylation withaluminum chloride by conducting the reaction in the presence of organicnitro compounds.

The primary purpose of this invention is to provide a direct alkylationmethod through the use of an inexpensive and readily available catalst,which method does not cause degradation of the polymer and its incidentreduction in molecular weight. A further purpose of this invention is toprovide a more useful alkylated polystyrene, and one which is especiallyeffective in improving the viscosity index of lubricating oils.

It has been found that if polystyrenes are al-- kylated using hydrogenfluoride as the catalyst unusually effective products are obtained.Although hydrogen fluoride is well known as a Friedel-Craft catalyst, itproduces a result quite different from that obtained by the prior artuse of aluminum chloride, and other catalysts usually used in thepreparation of alkylated polystyrene.

The alkylations are conducted in the manner well known to the prior art,except that hydrogen fluoride is used as catalyst for the reaction ofthe alkylating agent with the polystyrene in an inert solvent. Suitablealkylating agents are the olefinic hydrocarbons, such as propylene,isobutylene, cyclohexene, n-octadecene-l, polymeric propylene, polymericbutenes and other unsaturated hydrocarbons, the alkyl halides, such aspropyl chloride, butyl chloride, isobutyl chloride,

5 Clalmzu (Cl. 260-96) homologous chlorides of higher molecular weightcontaining up to 18 carbon atoms, and the corresponding fluorides,bromides and iodides; and the monounsaturated esters, such as methyloleate, oleyl acetate, lauryl oleate, oleyl stearate and homologuesthereof, especially those with a mono-unsaturated radical containin 8 to20 carbon atoms.

The polystyrene used in the practice of this invention is that withmolecular weight in excess of 10,000, and preferably in excess of60,000. Very high molecular weight polystyrene, for example those inexcess of 150,000, and up to 1,000,000, may be alkylated by this methodand are useful in specialized applications.

The reaction is preferably conducted in the presence of a suitablesolvent, for example nitro benzene, o-dichloro-benzene, chlorobenzeneand ethylene dichloride. The quantity of solvent may vary widely, thatamount being used which is necessary to produce a sufiicient fluidreaction mass. More solvent is generally required in the alkylation ofthe higher molecular weight polystyrenes.

The alkylations are generally conducted by charging a reaction vesselwith a solution of polystyrene and liquid hydrogen fluoride, and addingthe alkylating agent while stirring efficiently t contact the organicphase with the hydrogen fluoride catalyst phase. The reaction iscontinued until suflicient alkylation has taken place to render thepolystyrene soluble in the petroleum fraction to be modified. Preferredresults and good solubility in petroleum fractions are obtained by thesubstitution of an average of from 4 to 20 aliphatic carbon atoms perstyrene ring. After the desired degree of alkylation is achieved thehydrogen fluoride catalyst may be removed and recovered by distillation,and the polymer precipitated from the residual solution by mixing withalcohol, or other non-solvent for the alkylated polymer. If desired thealkylated polymer may be purified 'by resolution and reprecipitation.The polymer may also be obtained as a concentrated oil solution byadding the reaction mixture, after removal of hydrogen fluoride, to oiland distilling ofi the reaction solvent.

The alkylated polystyrenes prepared in accordance with this inventionare not significantly degraded and are unusually efiective in improvingthe viscosity index of lubricating oils, improving the tensile strengthof waxes, and improving the string and tackiness of greases.

Further details 01' the practice of this invention are set forth withrespect to the followin examples.

Example 1 A 1000 gram lot of a 10 percent solution of 85,000 averagemolecular weight polystyrene in ethylene dichloride and 80 grams ofliquid hydrogen fluoride were charged to a 1500 cc. stainless steelreactor fitted with an eflicient agitator and an opening for charging.The temperature was held at to 5 C. while 90 grams of a nonene fractionof olefins obtained by the polymerization of propylene were added over aperiod of two hours. Stirring was continued for an additional one andone-half hours. The hydrogen fluoride was removed and the polymersolution washed with water. The polymer was isolated by slowly addingthe solution to a large excess of ethanol while stirring vigorously. Onehundred seventy one grams of dry polymer were obtained.

Example 2 The alkylated polystyrene prepared in accordance with thepreceding example was dissolved in a solvent refined, 20 F. pour,mid-continent oil to the extent of one percent, and a sample 1 ofalkylated polystyrene was also prepared from the same polystyrene usingaluminum chloride as the alkylating catalyst. The following tabledemonstrates the measured 'viscosities at 100 F. and 210 F. on theuntreated oil sample and the identical oil containing one percent ofeach of the alkylated polystyrenes.

Vis. v15. 100 F. 210 F.

The above data demonstrate that polystyrene which has been alkylated byusing hydrogen fluoride is much more effective than is the same polymeralkylated by means of aluminum chloride.

Although the invention has been described with respect to specificembodiments, it is not intended that the details thereof shall beconstrued as limitations upon the scope of the invention except to theextent incorporated in the following claims.

Iclaim:

1. A method of preparing alkylated polystyrene which comprises reactingpolystyrene with a compound of the group consisting of hydrocarbonolefins, alkyl halides, and unsaturated aliphatic esters having a singleole'finic double bond and containing only carbon, hydrogen and oiwgen inthe presence of hydrogen fluoride.

2. A method of preparing alkylated polystyrene which comprisescontacting polystyrene with an olefinic hydrocarbon having from 3 to 30carbon atoms in the presence of hydrogen fluoride.

3. A method of preparing alkylated polystyrene which comprisescontacting polystyrene with an alkyl halide having from 3 to 30 carbonatoms in the presence of hydrogen fluoride.

4. A method of preparing alkylated polystyrene which comprisescontacting polystyrene with an unsaturated ester having an unsaturatedradical with from 8 to 20 carbon atoms, in the presence of hydrogenfluoride.

5. An alkylated polystyrene prepared by reacting polystyrene with acompound of the group consisting of hydrocarbon oleflns, alkyl halidesand unsaturated aliphatic esters having a single olefinic double bondand containing only carbon, hydrogen and oxygen in the presence ofhydrogen fluoride.

JOHN MANN BUTLER.

REFERENCES crrEn The following references are of record in the file ofthis patent:

UNITED STATES PA'I'ENTS OTHER REFERENCES Foster, The Oil and GasJournal, Jan. '7, 1943. Simo article in Ind. Eng. Chem., vol. 32. pages178-183.

1. A METHOD OF PREPARING ALKYLATED POLYSTYRENE WHICH COMPRISES REACTINGPOLYSTYRENE WITH A COMPOUND OF THE GROUP CONSISTING OF HYDROCARBONOLEFINS, ALKYL HALIDES, AND UNSATURATED ALIPHATIC ESTERS HAVING A SINGLEOLEFINIC DOUBLE BOND AND CONTAINING ONLY CARBON, HYDROGEN AND OXYGEN INTHE PRESENCE OF HYDROGEN FLUORIDE.